The present invention relates in general to the display of television pictures. More particularly, the invention relates to the display of a widescreen video image on widescreen and standard aspect ratio video monitors.
Color television pictures are broadcast in the United States according to the National Television System Committee (NTSC) composite standards. A television picture broadcast under the NTSC standard has an width-to-height or aspect ratio of 4:3. Visual information, however, is more often predominant in the horizontal direction than the standard 4:3 aspect ratio. The human eye also has a natural field of view that is significantly greater in the horizontal direction than the 4:3 aspect ratio.
To accommodate the natural characteristics of visual information and human vision, visual information has often been recorded and displayed in widescreen formats greater than 4:3. Motion pictures are commonly recorded in a 1.85:1 aspect ratio format. The Society of Motion Picture and Television Engineers favors a 16:9 aspect ratio as the standard for broadcast television. A 5:3 aspect ratio has also been proposed for broadcast television.
A primary issue with new widescreen aspect ratios is the compatibility of widescreen images with the millions of standard 4:3 aspect ratio televisions currently in use. A 16:9 widescreen image is 33.3% larger than a standard 4:3 image of the same vertical height. Widescreen motion pictures have been shown on broadcast television in a "letter box" to allow display of the entire image on a standard display monitor. The letter boxing of movies, however, has not been widely practiced because of mixed audience reception.
A more common method of achieving compatibility between widescreen and conventional pictures involves displaying only a 4:3 portion of the widescreen picture. A standard monitor thus displays a 4:3 "window" of the larger widescreen image. The widescreen image outside the 4:3 window, however, is not displayed. Thus, one approach to achieving compatibility involves broadcasting two television signals, one signal for widescreen televisions and a signal containing a 4:3 portion of the widescreen image for standard screens. The appropriate signal is chosen by the television receiver. Broadcasting two television signals, however, inefficiently consumes valuable transmission bandwidth. Another approach squeezes the widescreen image into the standard screen format. A 16:9 widescreen image is thus compressed into a 4:3 standard display. Compressing the widescreen image into the standard display, however, significantly distorts the image in the form of a lateral compression of the image.
Widescreen formats are also limited by available widescreen source material. Television programming today is ordinarily produced in the standard 4:3 format. As a result, many programs are not suitable for broadcast as a widescreen picture. Though conversion to a widescreen aspect ratio format is possible, the widescreen format is best utilized with widescreen source material.
Accordingly, there is a need for better utilization of widescreen aspect ratio images with standard aspect ratio display monitors.